a. Field of the Invention
The present invention relates generally to methods and apparatus for installing slipliners in pipes, and, more particularly, to an apparatus for installing a slipliner by advancing the slipliner into the pipe rather than by pulling it therethrough.
b. Related Art
Sliplining is a technique frequently used to renovate deteriorated pipes and pipelines, such as deteriorated concrete or steel water lines or sewers. The slipliner is typically formed of a plastic material such as high-density polyethylene (HDPE), and has an outside diameter somewhat smaller than the inside diameter of the old pipe so that a gap or “annulus” is formed between the two. In many or most installations, the annulus is filled with cement grout or other material after the slipliner has been put in place.
Although simple in concept, sliplining renovation has long posed a number of challenges from a practical standpoint. Amongst these is the difficulty of actually inserting the slipliner into the old, “host” pipe, often over distances of several hundred feet or more. The conventional approach has been to pull the slipliner into the host pipe, from one access opening towards another. However, this requires first running a cable through the host pipe so that tension can be applied to the end of the slipliner. The usual approach has been to attach a small string to a piece of wood or other float that is then carried through the host pipe by the flow of water/sewage. When the float reaches the next access opening, a slightly larger line is attached to the string and drawn through the host pipe in turn, with the process of being repeated with progressively larger lines and ropes until the actual tension cable can be pulled through to the other end. This process is tedious and grossly inefficient, as well as being highly unreliable: The chip/float or string may get stuck or caught along the way, and even if the attempt is successful, the string or smaller sizes of rope may abraid against damaged areas of the host pipe and part, so that the attempt must be repeated.
Moreover, although most slipliners are installed while water or sewage are flowing through them, there are situations where the host pipe may be “dry” and consequently have no flow for carrying a float and string therethrough. Under these circumstances, an alternative means must be found for threading the line through the host pipe; use of a robotic vehicle is one alternative, but is also slow and inefficient, and again potentially unreliable due to conditions in the deteriorated host pipe.
The delays and inefficiencies that are thus inherent in conventional “pull through” forms of slipliner installation are not inconsequential. To the contrary, they can represent many thousands or even hundreds of thousands of dollars in costs, especially for large projects, when wages, equipment costs, and son on are taken into account.
Accordingly, there exists a need for a method and apparatus for installing slipliners that does not require running a cable through the host pipe in order to pull the slipliner into place. Furthermore, there exists a need for such a method and apparatus that is capable of installing slipliners in a rapid manner. Still further, there exists a need for such a method and apparatus that is capable of installing a slipliner over long distances between access points. Still further, there exists a need for such a method and apparatus that is reliable and effective under field conditions.